1. Field of the Invention
The present invention relates to a method for controlling a sheet-to-sheet interval between a preceding sheet and a subsequent sheet in an image forming apparatus such as a laser beam printer, a copying machine, and an inkjet printer.
2. Description of the Related Art
Conventionally, an image forming apparatus includes a stacking unit for stacking recording media on which images have been formed. The image forming apparatus detects the amount of recording media stacked on the stacking unit, and if the detected amount exceeds a predetermined amount, the image forming apparatus determines that the recording media are fully stacked on the stacking unit. The image forming apparatus then stops performing the image forming process.
For example, Japanese Patent Application Laid-Open No. 2001-106426 discusses disposing a flag and a sensor in a discharge port of the stacking unit for detecting whether the recording media have passed through the discharge port. If the detected time for the recording media to pass through the discharge port is longer than a predetermined time, the image forming apparatus determines that the amount of the recording media stacked on the stacking unit has exceeded a predetermined amount. The image forming apparatus thus determines that the stacking unit is fully stacked.
However, in recent years, the number of sheets on which images are formed per unit time has been increased to improve productivity. For example, the sheets are conveyed by reducing a sheet-to-sheet interval that is an interval between a preceding sheet and a subsequent sheet. In such a case, there may not be enough time for confirming whether the recording media are fully stacked on the stacking unit depending on a response time of the sensor, i.e., a detection unit of the stacking unit. As a result, the image forming apparatus may incorrectly determine the fully-stacked state. For example, if the subsequent sheet reaches the flag before the status of the flag has changed after the preceding sheet has passed through the flag, an output from the sensor does not change. The image forming apparatus may thus falsely detect that the stacking unit is in the fully-stacked state even when the recording media are not fully stacked, and may stop performing the image forming process.